|  | Posted by afn03488 on 04/26/06 15:56 
Gene E. Bloch wrote:
 > If you recall the formula for the area of a circle, it is A = 4 pi  r-squared.
 
 As I recall, the area of a circle is just pi * r-squared
 
 > Thus a circle where r = 1, called a unit sphere,
 
 How does a planer shape become a solid? It is a unit circle, not a unit
 sphere.
 
 >  has an area  of 4 pi,
 
 No, it has an area of pi. Where did you find this factor of four?
 Are you confused with the formula for the volume of a sphere
 which is 4/3 * pi r-cubed
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